Capacitator terminal bushing with auxiliary sealing ring



March 3, 1953 D. E. GRAY 2,330,470

` CAPACITATOR TERMINAL vRUSHING W'ITH AUXILIARY SEALING RINGp Filed Feb.17, 19218 flrwmmf.

Patented Mar. 3, 1953 CAPACITATOR TERMINAL BUSHING WITH AUXILIARYSEALING RING Donald E. Gray, Teaneck, N. J., assignor toCornell-Dubilier Electric Corporation, S'outh Plainfield, N. J., acorporation of Delaware Application February 17, 1948, Serial No. 8,791

1 Claim.

This invention relates to improved terminal constructions particularlyadapted to be mounted on a closure or other portion of a container foran electrical capacitor. The terminals herein referred to are composedin large part of ceramic, such as porcelain, steatite or the like,usually having, as in common practice, a glazed outer surface. Suchterminals are fashioned to contain a liquid or semi-liquid dielectricsuch as mineral oil, chlorinated diphenyl or other oils or compounds. Inoperation, therefore, the terminal functions as a connecting point foran electrical circuit, as a seal for an aperture in the capacitorcontainer and also as a container for the liquid or semi-liquiddielectric which is contained within the terminal. Rigorous and testingconditions, such as are encountered in tropical climates and alongseacoasts, often give rise to failures in such terminals or to partialfailures which cause inefficient performance. Such failures resultbecause of difficulties encountered in sealing the various parts of theterminals to each other and to the container in which they are mounted.If the seals used are subject to deterioration because of climaticconditions or bei.

cause of physical shocks, air or moisture may enter the capacitorenclosure or the liquid dielectric contained in the terminal may leaktherefrom.

The general object of this invention is to pro- Vide an improvedtermina] construction particularly adapted to withstand rigorous serviceconditions. A specific object is to provide a sealed terminal structurewhich, at important joints, is provided with a protective double sealdesigned to give long and efficient life to the terminal and to thecapacitor assembly of which the terminal is a part.

Fig. 1 of the accompanying drawing is a side elevational view, partly insection, of a terminal constructed in accordance with this invention.

Fig. 2 is a partial view of the terminal shown in Fig. 1 and illustratesone modification which may be made in said terminal.

Referring to Fig. l, the terminal is shown in position on a cover I of asteel capacitor container II. It will be realized that whether theterminal be seated on the cover or on another wall of the container I Iis unimportant. Usually, however, the terminal is seated on the cover tofacilitate assembly. In the nal assembly of the capacitor the cover I0is welded or otherwise permanently affixed to the can i I. The terminalparts include the ceramic outer bushing I2, the ceramic inner bushing I3and the metallic connector cap I4, provided with means I5 for connection to an electrical circuit. The bushing I2 is shaped to provide aninner cavity in which is contained a liquid dielectric medium I6. Theterminal parts are held in assembled relation by the stud I'I, one endof which threads into the cap I4 and the other end of which is aiiiXedtc a holding disc I8. Connection of the stud I'I to the capacitorelements is conventional and is not shown. Since various types ofcapacitor bodies may be used with terminals, the capacitor elementswhich are placed within container II are not shown. After the porcelainbushings I2, I3 and the cap I4 have been assembled, as shown, on thecover I0 the dielectric I6 is introduced, through a hole I9 in the capI4 and thence through a corresponding channel 20, drilled in stud l'I,into the sealed chamber formed by the terminal assembly. Thereafter thehole I9 is sealed as, for instance, by a solder cap 2l.

Attention is now directed to the two joints in this terminal assemblywhich are exposed in the sense that they lie entirely or partiallyoutside of the container I I. The upper joint is between the metalliccap I4 and the upper end of the ceramic bushing I2. It will be notedthat if the capacitor be maintained upright as shown, failure of thisjoint will not allow leakage but will allow possible contamination, byatmosphere or moisture, of the contents of the terminal (but not of thecontents of the container II). The lower joint is, in eifect, betweenthe ceramic bushings I2 and I3 andthe cover I0. Failure of this jointwould allow drainage of the liquid dielectric I5 and also contaminationof the contents of container II by atmosphere or moisture. Further, itwill be noted that stresses applied to the ter minal assembly during usetend to concentrate in this lower joint.

As a step in the assembly of the terminal shown in Fig. 1, the outerceramic bushing I2 is provided, over the surface areas generallyindicated by brackets 22 and 23, with a thin metal coating, such asplatinum or silver. If desired, these metal coated areas may be tinnedor coated with another metal receptive to a selected solder. Prior toassembly there is also provided a rela tively thin metal cap washer 24perforated to loosely admit stud I'I. To prevent unnecessary corrosionhazards, it is advisable to form cap washer 24 from metal which is thesame as that used to make connector cap I4, usually copper. However,parts I4 and 24 may be formed of different materials, if desired. It ispreferred, but not necessary, to weld, solder or otherwise assemble capwasher 24 to cap i4 prior to final assembly of the terminal.

As the parts of the terminal are assembled on cover it in the positionshown, resilient sealing means, such as gaskets 25, 29 and 2l are proevided. These gaskets are preferably made of cork or other resilientmaterial of good body, and just prior to insertion into the assembly arepreferably painted or sprayed with a cement, such as a resin varnish,thereby insuring that the gaskets will be firmly sealed to adjoiningparts; viz., as to gasket 25, the bushing l2 and the cover I; as togasket 2li, the bushing I3 and the cover I9, and as the gasket 27, thebushing I3 and the metal disc I8.

After assembly is complete and the stud Il", the cap I4 and the disc I8have been adjusted to tightly hold the terminal parts together and tocompress the resilient members 25, 2S and 2l to form a leak proof seal,the depending edge of cap washer 24 is soldered to the surface oi thevbushing I2. The solder band 28 thus formed is built up upon themetallized surface which, as above described, had been originallyfurnished on the outer surface of the bushing. Thereafter, or previousthereto (the sequence being of no signiiicance to this invention) animpervious member, such as metal ring 29, is soldered or otherwise ixedto the previously inetallized wall of bushing l2, as indicated by thesolder band Sii. The depending edge of ring 29 is soldered to the coverlll, as indicated by the solder band 3l. To facilitate soldering of thedepending edge of ring 29 to the cover l0, it is preferred to emboss thecover with the depression 32 and to so proportion ring 29 that thedepending edge thereof extends into the depression 32 as shown.

. The thus constructed terminal is in effect sealed to the container IIwith a resilient double seal which has great eiiciency and tightnessunder the most adverse conditions of use. The outer sealing ring 29forms not only a complete seal but likewise a protective metal coverwhich protects the resilient gasket 25 against atmosphere, moisture andother agents or forces which in use may tend to age the resilientmaterial and thereby shorten its life as a sealing medium. Moreover, ifthe resilient gasket 25 should fail for any reason, a not unusual reasonbeing the aging effects of tropical temperatures or the effects ofeXtreme cold, thus allowing leakage of the dielectric medium i6, themedium will not escape but will ll the area 33 between ring 22 and coverIG and bushing l2, thereby forming an additional seal againstcontamination oi the contents of container H by minute. quantities ofgaseous contaminants which may pass through any porosity present insolder bands 3@ and 3i.

The seal provided by the cap washer 2t at the top of bushing I2 isparticularly effective because it is built entirely of metal and anyuneven seating of the top of bushing i2 against cap washer Eil as wouldtend to allow leakage of gaseous or liquid materials into the dielectricchamber is eiectively counteracted by the soldered down depending edgeof the cap washer which forms, in elect, a protective hood. However,this joint may, if desired, be constructed in various other ways withgood results, one convenient construction being shown in Fig. 2. In thatconstruction, which is otherwise similar to the terminal shown in Fig.1, the connecting cap 28 is fashioned with a depending rim 34 to form aseat for a resilient gasket 35. When, upon manipulation of stud 31, theparts are pulled firmly together and the gasket 35 pressed against theupper surface of bushing Sii, the edges of the gasket are protected bythe depending rim 34.

It will be understood that shapes of the parts shown in the variousgures and the materials of which they are made may vary withoutdeparture from the principles of this invention, except as indicated inthe appended claim.

Having thus described my invention, I claim:

A capacitor element comprising in assembled relation a capacitor wallhaving a terminal as- .sembly receiving aperture therein and a terminalassembly extending through and sealing said aperture, said terminalassembly including an inner ceramic bushing seated under said apertureand having a surface thereof disposed adjacent to and substantiallyparallel with the inner surface of said wall, a irst resilient sealingmember seated between and in sealing contact with the adjacentsubstantially parallel surfaces of said inner bushing and the innersurface of said wall, an outer ceramic bushing shaped to denne with saidinner bushing a liquid containable dielectric chamber, said outerbushing being seated over said aperture and bearing upon a secondresilient sealing member seated between and in sealing contactl with thesubstantially parallel surfaces of said outer bushing and the outersurface of said wall, a sealing cap seated upon the upper extremity ofsaid outer bushing, a cap washer disposed between said sealing cap andsaid outer bushing and having a dependent peripheral flange portionextending downwardly ver a portion of the surface of said outer bushning and ilxed thereto in hermetic sealing relation, means, including acircuit connecting member. positioned to maintain said terminal parts inassembled sealing relationship with the wall of the container and anexposed metal auxiliary sealing member disposed around a lower portionof the peripheral surface oi the outer bushing and extending downwardlyto the container wall, said member being xed to said peripheral surfacein hermetic sealing relationship, and fixed to said container wall inhermetic sealing relationship at a location remote from the terminalaperture therein to form a sealed space surrounding the sealingengagement between said bushings, said wall and the resilient membersinterposed therebetween.

DONALD E. GRAY.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 1,894,993 Jansson Jan. 24., 19331,910,226 Austin May 23, 1933 1,983,335 Austin Dec. 4, 1934 2,292,031Arnold Aug. 4, 1942 2,326,152 Marbury Aug. 10, 1943 2,411,656 Hendersonet al Nov. 26, 1946 2,434,554 Fields Jan. 13, 1948 2,499,769 Middleton,Jr. Mar. 7, 1950 2,598,184 Morisuye et al May 16, 1950 FOREIGN PATENTSNumber Country Date 914,120 France June ll, 1946

